1. Field of the Invention
The present invention relates to an apparatus for recording/reproducing a digital signal.
2. Description of the Related Art
In the field of professional-use video tape recorders (VTRs), demands for high video quality have shifted a VTR system from the conventional analog signal recording system to a digital signal recording system. The current digital VTR system is classified into a type of D1 format for dealing with a component video signal and a type of D2 format for dealing with a composite video signal. These formats permit four-channel digital audio signals to be recorded as well as the video signals. These signals can be recorded on different positions on the same track and individually edited.
From the feature of the above formats a digital audio signal can easily be edited among different channels using a single VTR. For example, such a VTR of a D1 format as disclosed in Hoso Gijutsu (Broadcasting Technology) Showa 61.11 (1986) pp. 72 to 76 has a digital audio precedingly reproducing head dedicatedly provided on a cylinder and can edit a digital signal among different channels with no signal delay. A precedingly reproduced signal can be used to realize various functions as well as the edition of audio signal. For example, a video signal precedingly reproduced from a VTR can be supplied to the same VTR to be recorded again after passed through an external device such as an effector. In a VTR in which video and audio signals are mixed and processed to provide a recording signal, part of the precedingly reproduced signal is rewritten and recorded.
When these functions are executed to record again the signal reproduced from a tape using the precedingly reproduced signal, the original signal recorded on the tape will be lost. This means that retrial is not permitted. These functions, therefore, must be executed very carefully. However, even when the greatest care is paid in executing these functions, as the case may be, the edition ends in failure because of inevitable causes such as the bad condition of the apparatus. This is a reason why these functions cannot be used with security. In order to obviate such difficulty, some mechanism for protecting the failure as well as means for executing these functions must be prepared.